I know I'm probably being paranoid, considering the vet checked Nero's eyes when we were there the day we got him, but I noticed that his left pupil always stays larger than his right pupil! They both will expand and shrink with the light, but that left one is always larger. Anything that would do that? Or is it just a quirk he's got?

It can be a symptom of Horner's Syndrome, which is inflammation of the nerve that controls the pupils and eyelids - but don't panic, it is not often caused by anything more serious than a bruise, the sort that cats can give each other when wrestling and neck grabbing. It can take several weeks or even as long as 6 months to go back to normal if it is that, and doesn't require treatment. If you've had him longer than that it could just be that he was born like it. It might be worth giving the vet a call to put your mind at rest Of course if accompanied with any other symptoms such as lethargy or lack of appetite then a vet visit is best.

He sure has no symptoms of lethargy or loss of appetite He's ALL over the place at the house running and tumbling and jumping. He also is eating regularly. I noticed the pupil the day we got him, after getting home from the vet.

I figured they would have mentioned something if there was a problem when they checked his eyes, but they basically gave him a good bill of health with the exception of the faint remnants of a URI from being at a shelter (which have gotten almost completely better since adoption on Monday too).

I am supposed to let them know how he is doing with the URI on the amoxicillan on Monday, so I probably will mention the pupil as well then, even though I'm not as 'worried' about it as I was anymore!

I know I'm probably being paranoid, considering the vet checked Nero's eyes when we were there the day we got him, but I noticed that his left pupil always stays larger than his right pupil! They both will expand and shrink with the light, but that left one is always larger. Anything that would do that? Or is it just a quirk he's got?

Hi Tara and Rob
My 14 y/o indoor girl has always had the left pupil larger than the right one-no medical problems, no issues- until approx 2 years ago, she had a seizure. I think only one or two. But who knows, I never witnesses it-I figured it out later.

Then last year she had a seizure (a large one) in my bed and I got to see it, scary!!! of course I took her to the vet-a homeopathic vet and he told me to avoid corn,soy,dairy and gave me some homeopathic stuff-adaposode/detoxosode/biosode and I found a herbal preparation for cats for seizures

No seizures for a year then about two weeks ago I changed her diet to something with corn in it, because all of a sudden she wouldnt eat the one I had been giving to her all along. Well, she ate the corn one and two weeks later had a seizure and this morn at 3am had another
we saw the vet again, blood work is fine. Only that pupil is larger than the other one and Im wondering if it has anything to do with these seizures

She is not showing symptoms or signs of a brain tumor, you would think she is totally healthy

About a month ago I noticed one of my cat's pupils was very slightly larger than the other but was not certain. Within the month I also noticed he had a tear or two. Once I realized that his pupil was indeed a little larger, I scheduled a vet appointment.

He has not acted any different - he eats, drinks, runs, and plays with the other kitty. The pupil even reacts to light/dark normally.

This morning the Vet examined my young male cat. First she checked his retinas which were fine - they acted perfectly normal. Then she took his blood pressure which was ok. Then she checked the pressure in each eye and found the normal eye was 20 and the abnormal eye was only 13. She told me 10 was an obvious problem so my cat was borderline. She called this anterior uveitis and gave me some steroid/antibiotic drops to give him 2x a day for 1 week

She also ran some blood and urine tests - results will come back on Monday.

My cat had Horner's syndrome and showed this. A deep ear infection was detected and antiobiotics and ear drops helped. Years later, one pupil is still a tad bigger than the other, but no one but me would notice.

My cat had Horner's syndrome and showed this. A deep ear infection was detected and antiobiotics and ear drops helped. Years later, one pupil is still a tad bigger than the other, but no one but me would notice.

Thank you! Funny thing is he often does something weird with his ear on that side - he sort of makes it sit halfway up. I mentioned this in the Vet's office and she saw it but shrugged it off. I'll suggest she look for an ear infection. Thank you!!!

One of Mitty's has always been slightly larger than the other. She's two years old now, and has no problems other than a slight heart murmer they found at her first vet trip. I don't know if it's related, but she's a healthy fiesty tortie.

My Callie-girl, who's about 13 yo, has this due to a cataract forming on her eye. It's been happening over the past 2 or 3 years. I don't think it bothers her, but it really freaks me out from time to time. I'd definitely mention it to the vet.

I'm taking Drake back to the Vet tomorrow because he still has one pupil larger than the other but now he is not acting like himself. He's being very antisocial, whiney, and he's staying in dark rooms. I'm seeing a different doctor this time and I'm going to suggest the ear infection like mentioned earlier in the post. If anyone has any other suggestions, please let me know. I find the pressure differences I mentioned in an earlier post peculiar but don't know what to make of it. Wish us luck in getting this resolved!

I really like the new Vet because we took Zoe in for peeing beside the litter box (like previous vet visits where they found nothing wrong) and she saw that Zoe's anal glands needed cleaned - between that and an antiobiotic it's like we have a brand new happy Zoe!

The new vet that examined Drake thought she saw a burst blood vessel in the bottom half of Drake's eye - the one with the larger pupil that would not respond to light as quickly or effectively.

Unfortunately this is usually caused by high blood pressure and his blood pressure has been fine during both visits.

Since she is not sure if it truly is a burst blood vessel or his normal color, and his blood pressure is fine, and he responded well to the steroid drops that we were using.....she said to go back to the drops but for 1 month this time instead of 1 week. Apparently this pupil thing is happening at random but vet's are seeing a positive response to the steroid.

Either way - if it continues to bother Drake and effect his personality, our next step is to see a opthamologist. I'll update in a month